1. Field of the Invention
The present invention relates to an apparatus for transferring toner images from a moving photoconductor to an image carrier which is fastened to a rotating cylinder.
2. Description of the Prior Art
When a toner image is transferred from a moving photoconductor to a moving image carrier, it is necessary to avoid any difference in speed between the photoconductor and the image carrier during the transfer operation, in order to obtain a high image quality. Generally, when the image carrier comprises paper, a plastic film or a similar material, transfer is effected with the aid of pressure heat and/or with the assistance of a corona discharge. As long as the thickness of the image carrier is always the same and in particular is so small that it is negligible compared to the radius of a cylinder on the circumference of which the photoconductor is mounted, there are hardly any problems of slip occurring between the photoconductor and the image carrier.
From U.S. Pat. No. 3,554,836 a transfer process for toner images is known, in which a toner image is developed on a silicone elastomer surface and is then transferred once or even more than once to further silicone elastomer surfaces and is eventually applied to the final image carrier, without splitting of the toner. In the process, an aluminum plate coated with a silicone elastomer may, for example, be used to form the shell of a roll, on which an image is present, which is developed by means of a developer. The developed image can subsequently be transferred to another roll which is also coated with a silicone elastomer and, from this roll, it is finally transferred to an image carrier web.
U.S. Pat. No. 4,092,925 describes an apparatus of a printing plate system comprising a recyclable printing member of aluminum to which a photosensitive coating is applied, which constitutes the image face together with the aluminum printing member. The aluminum printing member is supported by a carrier plate and is releasably connected thereto. Upon completion of the printing operation, the aluminum printing member is separated from the carrier plate which can also be reused.
In connection with the known apparatuses for the image transfer, the problem of synchronous running between the photoconductor and an image carrier which is mounted on a drum is not mentioned.